An ever increasing demand for greater bit capacity solutions drives the need to collocate a greater number of antennas within a single product housing or limited geographic area. As the number of collocated antennas increases, the number of possibilities with which the antennas may be mapped to one or more RF transceivers increases. Several different architectures are known. First, all of the collocated antennas may be connected to a single radio. Second, the collocated antennas may be divided between multiple radios operating in the same spectrum. Third, the collocated antennas may be divided between multiple radios operating in different frequency bands that are relatively close in frequency. Fourth, the collocated antennas may be divided between multiple radios operating in different frequency bands that are relatively far apart.
Some amount of antenna isolation (approximately 25 dB) is desired for each of the different architectures. However, each of the different architectures may have different requirements for antenna isolation to ensure desired system level performance, depending on how the collocated antennas are mapped to the transceiver(s). For example, the architecture that includes the collocated antennas divided between the multiple radios operating in the same spectrum requires the greatest antenna isolation between the collocated antennas connected to different radios because the different radios will otherwise inevitably interfere with one another.
When collocated antennas are divided between multiple radios, the most spatially effective and energy efficient way to achieve antenna isolation is to cross-polarize sets of antennas mapped to different radios. One set can be designed to radiate and receive vertically-polarized radiation, and another set can be designed to radiate and receive horizontally-polarized radiation. A greater polarization purity of antenna elements leads to a greater isolation between the sets of antennas.
Some antennas, such as the antenna disclosed in U.S. Pat. No. 8,963,793, are known in the art. However, known antennas with the above-identified architecture have at least two disadvantages. First, such known antennas include a complicated connection to a coaxial cable, including separate parts for feet or an eyelet, and a feed that is thermally tied to a substantial metal mass. Second, such known antennas are sensitive to radome loading at 2.4 GHz, thereby limiting products in which the antennas can reside.
In view of the above, there is a continuing, ongoing need for improved antennas.